Before she even started working at the University of Western Australia, Susan Marie had the idea for a creating a modern sundial in the back of her mind.

When she became the director of the UWA extension programme and the university began to centenary celebrations for 2013, the time seemed right to get the project underway.

"This building that it is on wasn't even built yet but it was a really good idea," Ms Marie said.

"We needed to find exactly the right time and place to put it, and we've done just that."

She first approached Dr Peter Kovesi, an engineer at the Centre for Exploration Targeting at UWA. He did the calculations for sundial which would use a west-facing wall to show not the clock time, but the number of hours before sunset, through sloping shadows on the wall.

He created a design which he describes as looking like "a wonky ladder."

"The central part is a series of calibrated lines that a gnomon, a horizontal rod projecting out from the sundial, that casts a shadow," Dr Kovesi explained.

"The position of the shadow on the mosaic starts off at the bottom of the sundial and as it gradually sets the shadow moves up and counts down the hours to sunset."

Called 'Hours to Sunset', the concept derives from the idea of 'Italian hours' which was used in Europe between the 14th and 18th centuries and which told workers how much daylight remained as the sun went down.

Dr Kovesi's pattern of lines was then passed onto award-winning artist Shaun Tan, who created the painting upon which the mosaic design for the sundial was based.

"The image was pixelated by a company in Italy and the artist there, in collaboration with Shaun Tan, matched the colours," said Ms Marie.

"They created the tiles in Italy and put them onto panels and very carefully shipped them out here."

"Our artisan tiler had to get them on the wall in a very precise way that didn't ruin the image or the calculations."

It was akin to transporting a very complicated and delicate jigsaw she said. Each tile is only 10mmx10mm, made of glass and there are about 368,000 of them making up the mosaic.

When the scaffolding finally came down a few weeks ago, it was a moment of triumph for most of the team but not for Peter Kovesi.

"Peter was slightly more agitated at this point because at that time his calculations came into play," Susan Marie said.

"This image had gone through a number of incarnations. Peter designed the sundial and then Shaun manipulated it and then it was sent off to Italy and then there was the tiling."

"But the lines and the Gnomon still needed to be exactly correct to tell the time. He was standing next to me, muttering under his breath, getting his car ready to flee Western Australia, never to be seen on the campus again."

"However, at five hours to sunset the shadow hit exactly the right place, there were wild cheers and the popping of champagne corks."

To relieve the accumulated tension, Peter Kovesi said he spent a few days in Albany paragliding.

'Hours to Sunset' is now on show on the west facing wall of University club building, and will be officially launched by Shaun Tan in April.

"I've not seen a sundial like this, of such scale and beauty, by such a celebrated artists anywhere," said Ms Marie.

"It's a wonderful piece of Western Australian history. It's hard to do public art that's got such meaning for a place and the people in it, and I think this one sort of ticks all those boxes."